Hey,
So I would like to start off by saying this was a good start to a story; the opening chapter is always important and you wrote it really well so well done.
I haven't read many of the pregnant-at-Hogwarts storys but your beginning is great so I'm sure it will make a great story; your characters are great and you have room to make them even better, and your descriptions too! So well done for that.
Just one tip would be to keep an eye on grammer (I notice because I know my grammer often goes weird) so if you want to improve on that you could reread chapters you've written or use spelling/grammer check.
Other than that well done and continue doing this good.
Happy Writing.
~Char